Sahih Muslim Book 26, Hadith Number 5506.

Chapter : Plague, ill omen and magic.

‘Amir b. Rabi’ah reported: ‘Umar went to Syria and as he came to Sargh, information was given to him that an epidemic had broken out in Syria. ‘Abd al-Rahman b. ‘Auf narrated to him that Allah’s Messenger (may peace be upon him) had said: When you hear of its presence in a land, don’t move towards it, and when it breaks out in a land and you are therein, then don’t run away from it. So ‘Umar b. Khattab came back from Sargh. Salim b. ‘Abdullah reported that ‘Umar went back, along with people on hearing the hadith reported on the authority of ‘Abd al-Rahman b. ‘Auf.